Conventional oil and gas drilling techniques produce economical quantities of hydrocarbons when performed on porous formations. Often, when a wellbore penetrates a porous formation, oil and gas flow into the low-pressure region created by the wellbore. However, less porous formations, also known as tight formations, can be inaccessible using conventional methods. Because oil and gas cannot easily flow through tight formations in economic quantities, such tight formations cannot usually be completed economically using only conventional completion techniques.
Previous methods of hydraulic fracturing allow impermeable formations to produce oil and gas in economic quantities. Generally, hydraulic fracturing methods pump a fluid into a formation at a pressure sufficient to cause the formation to fracture, thereby creating primary fractures. The primary fractures in the formation increase the effective porosity of the formation and allow for the economic production of hydrocarbons. When fluid under high pressure, such as the fracturing fluid, encounters pores in the underground formation, the fluid can enter the network of pores in the underground formation.
The entry of fluids into the pore network of a formation can have a deleterious effect on production, especially on formations comprising clays and water sensitive clays. The entry of fluids into such formations can cause the clay to swell, slough, degrade, release fines, or become ductile. The chemical and physical changes to the minerals often result in the blockage or closure of passageways that penetrate the subterranean formation, thereby causing a loss in permeability of the formation.
This loss in permeability impairs the flow of fluid through the wellbore and, in some cases, may even completely block the flow of fluids through portions of the formation. Loss in permeability often leads to a decrease in the production for the well. Moreover, some changes in the minerals may lead to sloughing, which yields fines capable of migrating and being produced with the formation fluids, thereby presenting potential abrasion and other problems with the production equipment and potential reduction in fracture conductivity.